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Conic Sections: Ellipse, Parabola and Hyperbola

Meet the three curves a plane cuts from a cone, in both their locus definitions and their standard equations, and read foci and axes off the equation.

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What a learner can do afterwards

  • Match each standard equation to its curve and identify centre, axes and foci
  • State the distance property that defines an ellipse, a parabola and a hyperbola
  • Recognise a conic from a shifted equation by completing the square in both variables

1 · Read

Every conic is a slice of a cone, and the slicing angle decides the curve. A gentle tilt gives an ellipse, a slice parallel to the side gives a parabola, and a steep cut through both halves gives a hyperbola. Equations show the same split: plus between the squares means ellipse, minus means hyperbola, and a single squared variable means parabola.

Each curve also owns a distance rule. An ellipse fixes the sum of the distances to two foci. A parabola matches one focus to a line called the directrix, point for point. A hyperbola fixes the difference of the distances to two foci.

Try it together

Read x squared over 25 plus y squared over 9 equals 1. Both signs are positive with unlike denominators, so it is an ellipse with a equal to 5 along x, and its vertices are (5, 0) and (minus 5, 0). For the hyperbola x squared over 16 minus y squared over 9 equals 1, c squared equals 16 plus 9, so c equals 5. For the parabola y squared equals 12x, 4p equals 12, so the focus sits 3 units from the vertex.

Good to know

If squares come expanded with extra x or y terms, complete the square in each variable to reveal the shifted centre. The ellipse (x minus 1) squared over 4 plus (y plus 2) squared over 9 equals 1 centres at (1, minus 2), since x minus 1 and y plus 2 set the shifts.

Angle of slice picks the curve, distance rule defines it, and the equation pattern names it.

More to read

7.5 Conic Sections

Every conic is a slice of a cone, and the slicing angle decides the curve. A gentle tilt gives an ellipse, a slice parallel to the side gives a parabola, and a steep cut through both halves gives a hyperbola. Each curve also owns a distance property: ellipses fix the sum of distances to two foci, parabolas match one focus to a line, hyperbolas fix the difference. Standard equations wear these facts openly: denominators reveal the axes and the focus offset falls out of a squared sum or difference.

12.2 The Hyperbola

A hyperbola is the set of points whose distances from two foci differ by a fixed amount. Its equation splits x and y with a minus sign, and the positive term points along the transverse axis. From a squared minus b squared come the vertices, and c squared equals a squared plus b squared locates the foci. Asymptotes are the diagonals of the central box and steer the branches at a distance. Sketch box first, asymptotes second, branches last.

Conic sections: FAQ

Sorting conics fast comes down to pattern spotting. Two squared terms with the same sign and different denominators signal an ellipse, equal denominators a circle. A minus between the squares means hyperbola, and a single squared variable means parabola. Centres and vertices read straight off once the equation is in standard form. If squares are expanded with x or y terms attached, complete the square in each variable to reveal the shifted centre.

Introduction to Analytic Geometry

Analytic geometry joins algebra to pictures through the coordinate plane. Every point becomes a pair of numbers and every curve becomes an equation those pairs satisfy. Distance and midpoint formulas turn shapes into calculations you can check by hand. Conics show one framework describing circles, ellipses, parabolas, and hyperbolas together. Master completing the square here and the whole chapter gets easier.

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2 · Watch

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Take it off screen

Print a worksheetA4 with an answer key page for grown-ups. No screen, no internet.

Where it sits

Where this leads

Jobs that lean on this skill. Follow one to see everything it is built on.

Then practise

14 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.

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Conic Sections: Ellipse, Parabola and Hyperbola · Mathematics, ages 17 to 18 · LightMySky